Torque3D/Engine/source/persistence/rapidjson/encodedstream.h

#ifndef RAPIDJSON_ENCODEDSTREAM_H_
#define RAPIDJSON_ENCODEDSTREAM_H_

#include "rapidjson.h"

namespace rapidjson {

//! Input byte stream wrapper with a statically bound encoding.
/*!
	\tparam Encoding The interpretation of encoding of the stream. Either UTF8, UTF16LE, UTF16BE, UTF32LE, UTF32BE.
	\tparam InputByteStream Type of input byte stream. For example, FileReadStream.
*/
template <typename Encoding, typename InputByteStream>
class EncodedInputStream {
	RAPIDJSON_STATIC_ASSERT(sizeof(typename InputByteStream::Ch) == 1);
public:
	typedef typename Encoding::Ch Ch;

	EncodedInputStream(InputByteStream& is) : is_(is) { 
		current_ = Encoding::TakeBOM(is_);
	}

	Ch Peek() const { return current_; }
	Ch Take() { Ch c = current_; current_ = Encoding::Take(is_); return c; }
	size_t Tell() const { return is_.Tell(); }

	// Not implemented
	void Put(Ch c) { RAPIDJSON_ASSERT(false); }
	void Flush() { RAPIDJSON_ASSERT(false); } 
	Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
	size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }

private:
	// Prohibit assignment for VC C4512 warning
	EncodedInputStream& operator=(const EncodedInputStream&);

	InputByteStream& is_;
	Ch current_;
};

//! Output byte stream wrapper with statically bound encoding.
/*!
	\tparam Encoding The interpretation of encoding of the stream. Either UTF8, UTF16LE, UTF16BE, UTF32LE, UTF32BE.
	\tparam InputByteStream Type of input byte stream. For example, FileWriteStream.
*/
template <typename Encoding, typename OutputByteStream>
class EncodedOutputStream {
	RAPIDJSON_STATIC_ASSERT(sizeof(typename OutputByteStream::Ch) == 1);
public:
	typedef typename Encoding::Ch Ch;

	EncodedOutputStream(OutputByteStream& os, bool putBOM = true) : os_(os) { 
		if (putBOM)
			Encoding::PutBOM(os_);
	}

	void Put(Ch c) { Encoding::Put(os_, c);  }
	void Flush() { os_.Flush(); }

	// Not implemented
	Ch Peek() const { RAPIDJSON_ASSERT(false); }
	Ch Take() { RAPIDJSON_ASSERT(false);  }
	size_t Tell() const { RAPIDJSON_ASSERT(false);  return 0; }
	Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
	size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }

private:
	// Prohibit assignment for VC C4512 warning
	EncodedOutputStream& operator=(const EncodedOutputStream&);

	OutputByteStream& os_;
};

#define RAPIDJSON_ENCODINGS_FUNC(x) UTF8<Ch>::x, UTF16LE<Ch>::x, UTF16BE<Ch>::x, UTF32LE<Ch>::x, UTF32BE<Ch>::x

//! Input stream wrapper with dynamically bound encoding and automatic encoding detection.
/*!
	\tparam CharType Type of character for reading.
	\tparam InputByteStream type of input byte stream to be wrapped.
*/
template <typename CharType, typename InputByteStream>
class AutoUTFInputStream {
	RAPIDJSON_STATIC_ASSERT(sizeof(typename InputByteStream::Ch) == 1);
public:
	typedef CharType Ch;

	//! Constructor.
	/*!
		\param is input stream to be wrapped.
		\param type UTF encoding type if it is not detected from the stream.
	*/
	AutoUTFInputStream(InputByteStream& is, UTFType type = kUTF8) : is_(&is), type_(type), hasBOM_(false) {
		DetectType();
		static const TakeFunc f[] = { RAPIDJSON_ENCODINGS_FUNC(Take) };
		takeFunc_ = f[type_];
		current_ = takeFunc_(*is_);
	}

	UTFType GetType() const { return type_; }
	bool HasBOM() const { return hasBOM_; }

	Ch Peek() const { return current_; }
	Ch Take() { Ch c = current_; current_ = takeFunc_(*is_); return c; }
	size_t Tell() const { return is_->Tell(); }

	// Not implemented
	void Put(Ch) { RAPIDJSON_ASSERT(false); }
	void Flush() { RAPIDJSON_ASSERT(false); } 
	Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
	size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }

private:
	// Detect encoding type with BOM or RFC 4627
	void DetectType() {
		// BOM (Byte Order Mark):
		// 00 00 FE FF  UTF-32BE
		// FF FE 00 00  UTF-32LE
		// FE FF		UTF-16BE
		// FF FE		UTF-16LE
		// EF BB BF		UTF-8

		const unsigned char* c = (const unsigned char *)is_->Peek4();
		if (!c)
			return;

		unsigned bom = c[0] | (c[1] << 8) | (c[2] << 16) | (c[3] << 24);
		hasBOM_ = false;
		if (bom == 0xFFFE0000)					{ type_ = kUTF32BE; hasBOM_ = true; is_->Take(); is_->Take(); is_->Take(); is_->Take(); }
		else if (bom == 0x0000FEFF)				{ type_ = kUTF32LE;	hasBOM_ = true;	is_->Take(); is_->Take(); is_->Take(); is_->Take();	}
		else if ((bom & 0xFFFF) == 0xFFFE)		{ type_ = kUTF16BE; hasBOM_ = true; is_->Take(); is_->Take();							}
		else if ((bom & 0xFFFF) == 0xFEFF)		{ type_ = kUTF16LE; hasBOM_ = true; is_->Take(); is_->Take();							}
		else if ((bom & 0xFFFFFF) == 0xBFBBEF)	{ type_ = kUTF8;	hasBOM_ = true; is_->Take(); is_->Take(); is_->Take();				}

		// RFC 4627: Section 3
		// "Since the first two characters of a JSON text will always be ASCII
		// characters [RFC0020], it is possible to determine whether an octet
		// stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking
		// at the pattern of nulls in the first four octets."
		// 00 00 00 xx  UTF-32BE
		// 00 xx 00 xx  UTF-16BE
		// xx 00 00 00  UTF-32LE
		// xx 00 xx 00  UTF-16LE
		// xx xx xx xx  UTF-8

		if (!hasBOM_) {
			unsigned pattern = (c[0] ? 1 : 0) | (c[1] ? 2 : 0) | (c[2] ? 4 : 0) | (c[3] ? 8 : 0);
			switch (pattern) {
			case 0x08: type_ = kUTF32BE; break;
			case 0x0A: type_ = kUTF16BE; break;
			case 0x01: type_ = kUTF32LE; break;
			case 0x05: type_ = kUTF16LE; break;
			case 0x0F: type_ = kUTF8;    break;
			}
		}

		// RUntime check whether the size of character type is sufficient. It only perform checks with assertion.
		switch (type_) {
		case kUTF8:
			// Do nothing
			break;
		case kUTF16LE:
		case kUTF16BE:
			RAPIDJSON_ASSERT(sizeof(Ch) >= 2);
			break;
		case kUTF32LE:
		case kUTF32BE:
			RAPIDJSON_ASSERT(sizeof(Ch) >= 4);
			break;
		}
	}

	typedef Ch (*TakeFunc)(InputByteStream& is);
	InputByteStream* is_;
	UTFType type_;
	Ch current_;
	TakeFunc takeFunc_;
	bool hasBOM_;
};

//! Output stream wrapper with dynamically bound encoding and automatic encoding detection.
/*!
	\tparam CharType Type of character for writing.
	\tparam InputByteStream type of output byte stream to be wrapped.
*/
template <typename CharType, typename OutputByteStream>
class AutoUTFOutputStream {
	RAPIDJSON_STATIC_ASSERT(sizeof(typename OutputByteStream::Ch) == 1);
public:
	typedef CharType Ch;

	//! Constructor.
	/*!
		\param os output stream to be wrapped.
		\param type UTF encoding type.
		\param putBOM Whether to write BOM at the beginning of the stream.
	*/
	AutoUTFOutputStream(OutputByteStream& os, UTFType type, bool putBOM) : os_(&os), type_(type) {
		// RUntime check whether the size of character type is sufficient. It only perform checks with assertion.
		switch (type_) {
		case kUTF16LE:
		case kUTF16BE:
			RAPIDJSON_ASSERT(sizeof(Ch) >= 2);
			break;
		case kUTF32LE:
		case kUTF32BE:
			RAPIDJSON_ASSERT(sizeof(Ch) >= 4);
			break;
		case kUTF8:
			// Do nothing
			break;
		}

		static const PutFunc f[] = { RAPIDJSON_ENCODINGS_FUNC(Put) };
		putFunc_ = f[type_];

		if (putBOM)
			PutBOM();
	}

	UTFType GetType() const { return type_; }

	void Put(Ch c) { putFunc_(*os_, c); }
	void Flush() { os_->Flush(); } 

	// Not implemented
	Ch Peek() const { RAPIDJSON_ASSERT(false); }
	Ch Take() { RAPIDJSON_ASSERT(false); }
	size_t Tell() const { RAPIDJSON_ASSERT(false); return 0; }
	Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
	size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }

private:
	void PutBOM() { 
		typedef void (*PutBOMFunc)(OutputByteStream&);
		static const PutBOMFunc f[] = { RAPIDJSON_ENCODINGS_FUNC(PutBOM) };
		f[type_](*os_);
	}

	typedef void (*PutFunc)(OutputByteStream&, Ch);

	OutputByteStream* os_;
	UTFType type_;
	PutFunc putFunc_;
};

#undef RAPIDJSON_ENCODINGS_FUNC

} // namespace rapidjson

#endif // RAPIDJSON_FILESTREAM_H_